The present invention relates to a process of manufacturing a compound semiconductor, relates to a dry etching method for fabricating an InP or epitaxially grown thin film thereof with satisfactory controllability and anisotropically, and particularly relates to a dry etching method and apparatus using ions generated by an induction coupling plasma (ICP) source or plasma having a high frequency in bands of VHF, UHF, and the like.
Etching fabrication techniques for a compound semiconductor are used for manufacturing various compound semiconductor elements such as a semiconductor laser and an optical modulator. Though wet etching has been employed for etching of a compound semiconductor for a long time, increasing demand for improvement in uniformity of fabrication dimensions in wafer surfaces in recent years has promoted studies of dry etching techniques.
Because of demand for miniaturization of, and dry processes for, such compound semiconductor devices, etching techniques superior in microfabrication properties and selectivity of types of material, and controllability of high-speed processes or etching shapes have become particularly important in processes of manufacturing HBT (Heterojunction Bipolar Transistor), HEMT (High Electron Mobility Transistor) and the like that have been increasing in performance with miniaturization.
As dry etching methods for a compound semiconductor as prior art have been used reactive ion etching (RIE), reactive ion beam etching (RIBE), and the like with use of mixed gas of chlorine-based gas and an inert gas such as argon, mixed gas of methane or halomethane and hydrogen, or the like.
Control of anisotropy of fabrication shape, however, requires supply of considerable electric power, which may cause plasma damage on surfaces of substrates or thin films and may make it difficult to ensure flatness (specularity) of the surfaces.
For via hole fabrication that is extremely important for high-speed operation (electron mobility) of HEMT devices using InP, on the other hand, deep etching fabrication is required, for example, with a depth of at least not less than 20 μm, more preferably, not less than 100 μm. In other words, a highly selective process is required and high-speed etching is indispensable for a resist mask; however, it is difficult to perform such treatment within a desired period of time with RIE plasma of the mixed gas of methane or halomethane and hydrogen. In addition, it has conventionally been difficult to obtain satisfactory fabrication shapes in etching of InP material with chlorine-based gas, because a vapor pressure of chloride of In has been low.
Therefore, an object of the present invention is to solve issues described above and to provide a dry etching method and apparatus that are capable of performing deep etching fabrication rapidly on a substrate of an InP-based compound semiconductor.